Gas turbine engines typically become more efficient with higher turbine inlet gas temperatures. However higher turbine inlet gas temperatures necessitate increased cooling of the turbine components.
It has been known to provide a heat exchanger located in low pressure areas of the engine or outside of the engine casing, where fuel is put into heat exchange relationship with the pressurized air from the combustor to heat the fuel before combustion and cool the pressurized air surrounding the high pressure turbine. Such heat exchanger typically require a high pressure casing to contain the pressurized air and relatively heavy air ducts to circulate the pressurized air to and from the heat exchanger.